From: Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>
When a breakpoint or trap happens when operating in kernel mode but
on users behalf (eg syscall) it is necessary to change the address
limit to KERNEL_DS so any address checking can be bypassed and print
the correct stack trace.
Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>
Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
---
arch/mips/kernel/traps.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 3e5e700..a5a74d6 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -862,6 +862,11 @@ asmlinkage void do_bp(struct pt_regs *regs)
enum ctx_state prev_state;
unsigned long epc;
u16 instr[2];
+ mm_segment_t seg;
+
+ seg = get_fs();
+ if (!user_mode(regs))
+ set_fs(KERNEL_DS);
prev_state = exception_enter();
if (get_isa16_mode(regs->cp0_epc)) {
@@ -921,6 +926,7 @@ asmlinkage void do_bp(struct pt_regs *regs)
do_trap_or_bp(regs, bcode, "Break");
out:
+ set_fs(seg);
exception_exit(prev_state);
return;
@@ -934,8 +940,13 @@ asmlinkage void do_tr(struct pt_regs *regs)
u32 opcode, tcode = 0;
enum ctx_state prev_state;
u16 instr[2];
+ mm_segment_t seg;
unsigned long epc = msk_isa16_mode(exception_epc(regs));
+ seg = get_fs();
+ if (!user_mode(regs))
+ set_fs(get_ds());
+
prev_state = exception_enter();
if (get_isa16_mode(regs->cp0_epc)) {
if (__get_user(instr[0], (u16 __user *)(epc + 0)) ||
@@ -956,6 +967,7 @@ asmlinkage void do_tr(struct pt_regs *regs)
do_trap_or_bp(regs, tcode, "Trap");
out:
+ set_fs(seg);
exception_exit(prev_state);
return;
--
1.8.5.3
